A potentially season ending ankle injury for Tomas O’Leary marred Munster’s tenth straight win in all competitions, which saw the Magners League leaders outscore the Scarlets by four tries to one at Musgrave Park.

Early indications are that scrum half Tomas O’Leary, one of eight Munster players included in the British & Irish Lions squad, has a suspected fractured ankle.

He was immediately ruled out of next weekend’s Heineken Cup semi-final showdown with Leinster, while, depending on scan results, his chances of recovering for South Africa seem extremely slim.

In a Magners League context, tries from Ian Dowling, David Wallace, Keith Earls and Denis Leamy helped table toppers Munster move onto 58 points.

That means if the Ospreys have a pointless return against Edinburgh on Saturday, the league title will be Munster’s.

The reigning European champions had seven of their eight 2009 Lions on board, with tour captain Paul O’Connell the only absentee as he rested a sore hip.

Lions duo Matthew Rees and Stephen Jones filled places on the Scarlets bench, with Nigel Davies giving a number of the region’s young talents a run-out.

The Scarlets bossed possession from the off but Rhys Priestland failed to follow up on some good early work when he flashed a third-minute penalty wide of the target.

Munster roared back and from their first real attack on 6 minutes, Earls and Doug Howlett rampaged up the right, Lifeimi Mafi then sucked in three defenders before O’Leary scooped a long pass out to the left for Dowling to score on the overlap.

O’Gara converted but just two minutes later, as the Scarlets gained ground into the Munster 22, an unfortunate collision between Wallace and O’Leary saw the scrum half go over on his left ankle and he had to be stretchered off.

Priestland landed a subsequent penalty but a retreating scrum was really hampering the Scarlets, albeit with their lineout holding up well.

Both Daniel Evans and Priestland kicked well for position but good cameos from Alan Quinlan and Dowling adding urgency to Munster’s play and Earls was held up over the try-line shortly afterwards, as Jon Davies came in with a timely intervention.

After a series of creaking Scarlets scrums, Lee Williams put in a crucial hit on Paul Warwick but that defensive work wore down the visitors and Wallace spun past an initial tackle and powered his way over for a 33rd-minute try.

O’Gara’s conversion left some daylight between the sides at 17-3 at half-time, although Earls was the unlucky player to receive time in the sin-bin after a series of ruck infringements from both sides.

The Scarlets brought on Rees, Jones and Phil John for the second half, setting up a potential Lions number 10 duel between Jones and O’Gara but that never materialised in a stop-start final 40 minutes.

The changes did help the Welshmen grab a try, five minutes in, when Williams cantered into space on the right and linked with the supporting Evans before busy scrum half Roberts took the scoring pass and dotted down from close range.

Roberts’ fifth league try was converted by Jones for 17-10 but five minutes later, Roberts received a yellow for leaving a trailing boot as Peter Stringer tried to put Munster through on an overlap.

Tony McGahan’s men took their cue. Upping the pace with Jerry Flannery and Leamy prominent throughout, Mafi put Earls through for a simple try, converted by O’Gara, and then Leamy pounced off the back of a steamrolling scrum to chalk up the bonus point.

That extra point puts defending champions Leinster out of the title race and effectively ended the match as a contest, with Mafi becoming the third player to be sin-binned in a scrappy finish.